High prevalence of OXA-48-like and NDM carbapenemases among carbapenem resistant Klebsiella pneumoniae of clinical origin from Iran.

BACKGROUND AND OBJECTIVES: Klebsiella pneumoniae is increasingly developing resistance to last-resort antibiotics such as carbapenems. This study aimed to investigate the dissemination of common carbapenemase encoding genes among 48 clinical isolates of carbapenem-resistant Klebsiella pneumoniae (CRKP).

MATERIALS AND METHODS: Antimicrobial susceptibility testing was performed by broth dilution and disc diffusion methods. The phenotypic evaluation of carbapenemase production was performed by using Modified Carbapenem Inactivation Method. Presence of carbapenemase encoding genes bla KPC , bla NDM , bla OXA-48-like , bla IMP , and bla VIM was screened by PCR.

RESULTS: Overall, carbapenemases were produced in all CRKP isolates. The bla OXA-48-like and bla NDM were the most prevalent genes detected among all and 66.6% (n=32) of CRKP isolates respectively. The bla VIM was detected in only one isolate co-harboring NDM and OXA-48-like carbapenemases. The bla KPC and bla IMP genes were not identified in any of the isolates. While tigecycline was the most active agent against CRKP isolates with low resistance rate (4.1%), high rate of resistance was observed to colistin (66.6%), amikacin (79%) and most of other tested antimicrobials.

CONCLUSION: Our results revealed predominant prevalence of OXA-48-like and NDM carbapenemases among CRKP clinical isolates. High rate of resistance to last-resort agents such as colistin among CRKP isolates is a source of great concern.